Telecommunication systems



Nov. 25, 1958 A. DAVISON ETAL 2,862,149

' TELECOMMUNICATION SYSTEMS Original Filed Jan. 12, 1953 AL'AN DAV/SON.

RONALD THREADGOLD.

Inventors Attorneys rELEconmUNIcAnoN SYSTEMS Original application January 12, 1953, Serial No. 330,638. Divided and this application February 26, 1957, Serial No. 642,462

6 Claims. (Cl. 315-345) This application is a division of copending application Serial No. 330,638 filed on January 12, 1953.

The present invention relates to multi-stage circuit arrangements or hunting circuits having a gas discharge tube for each stage and each stage being associated with a piece of equipment which applies a marking potential to the stage if it is available for selection.

The object of the invention is to provide an improved high-speed multi-stage circuit arrangement or hunting circuit which has many applications in the field of automatic telephony.

According to one feature of the invention, in a multistage circuit arrangement having a gas discharge tube in each stage and each stage being associated with a piece of equipment which applies a marking condition to the stage if it is available for selection the stages are connected in cascade and the gas discharge tubes are arranged to strike successively each, except the tube of the first stage, in response to the striking of the gas discharge tube of the preceding stage and subject to the marking condition which is applied individually to a stage and which inhibits the striking of a gas discharge tube thereby preventing the successive striking of subsequent gas discharge tubes.

According to a further feature of the invention, in a multi-stage hunting circuit having a gas discharge tube in each stage and each stage being associated with a piece of equipment which applies a marking condition to the stage if it is available for selection the stages are connected in cascade and a potential applied to one stage of the circuit is repeated from stage to stage by the successive striking of a gas discharge tube in each stage and only at a stage to which a marking condition has been circuit for taking into use the first idle one of a plurality of pieces of equipment. The circuit consists of a plurality of similar stages, one for each piece of equipment. For convenience, however, the drawing only shows the first and last stage. The first stage comprises the three tubes VK20, VK21 and VK22 while the last stage similarly arranged tubes VK30, VK31 and VK32. Leads such as 20 and 30 extend individually to the pieces of equipment and if the latter are available, a positive marking potential is applied to the associated lead. Thus if the equipment associated with lead 20 is available, the positive marking potential thereon will serve to bias the tube VK20. When the hunting operation is to take place, a pulse is applied to lead 22, which is connected via capacitors such as C20 and C30. Those tubes strike which are positively biased over the lead such as 20 and tes Patent 2,862,149 Patented Nov. 25, 1958 it will first be assumed that the equipment associated with lead 20 is available. Tube VK20 will therefore strike and a positive voltage will be developed at the junction of the two cathode resistors R20 and R21. Resistor R21 forms, together with resistor R22, the cathode load of tube VK21 so that the positive voltage at the junction of resistors R20 and R21 serves to back off tube VK21. The same positive voltage, however, serves to apply via resistor R23 a positive biasing potential to the trigger electrode of tube VK22. In addition when tube VK20 strikes it causes the diode VN20 to strike whereby a positive potential is applied from resistor R24 to the pulse delay circuit which then applies a delayed pulse to the trigger electrodes of tubes VK21 and VK22. Only tube VK22 strikes, however, since tube VK21 is backed 011 as described above. Tube VK22 in striking applies a positive potential to lead 21 which is connected to the associated piece of equipment and this positive potential serves to take into use the piece of equipment whereupon the positive potential is removed from lead 20. When the piece of equipment has been taken into use, means (not shown) become effective to extinguish the conducting tubes in the hunting circuit.

Now assume that the piece of equipment associated with lead 20 is unavailable when the hunting operation is initiated but that at least one of the other pieces of equip ment is available. When the hunting operation is initiated, tube VK20 will not strike but at least one of the tubes corresponding to VK20 and which is associated with an available piece of equipment will strike so that a positive potential is developed in resistor R24 on the striking of the associated diode. The pulse applied by the pulse delay circuit PD to the tubes VK21 and VK22 now causes tube VK21 to strike since this tube is not backed oif but tube VK22 does not strike since no positive biasing potential is applied to its trigger electrode. Tube VK21 in striking applies a positive pulse to the two tubes of the next stage which correspond to tubes VK21 and VK22 of the first stage. One or other of these tubes will strike according to the condition of the associated piece of equipment and if it is available, it will be taken into use while if it is unavailable a pulse will be repeated to the next stage. This operation continues until an idle piece of equipment is found.

We claim:

1. An electronic hunting arrangement for bringing into use a first available one of a plurality of pieces of equipment, comprising a plurality of successive stages, one stage for each piece of equipment, each of said stages comprising a plurality of gas-filled tubes, each of said tubes having a plurality of principal electrodes, a lead extending from a first one of said plurality of tubes to a corresponding piece of equipment to provide a marking potential biasing said first tube, means for applying a pulse to said lead causing said first tube to strike if said corresponding piece of equipment is available to provide a potential to a principal electrode of a second and a third tube of said plurality of tubes, a pair of resistors connected between said first tube and said second and third tubes to apply the potential developed at said first tube to a principal electrode of said second tube biasing this tube to nonconductance and said potential applied to a principal electrode of said third tube to trigger said electrode. and render said third tube conductive, means responsive to the striking of said first tube to apply a pulse to said second and third tubes and thereby cause the said third tube to strike, and said last-mentioned pulse being insufiicient to overcome the bias on said second tube leaving said second tube nonconductive, said third tube being connected to the associated piece of equipment to take the piece of equipment into use and 3 remove the potential from said first mentioned lead when said third tube strikes.

2. The electronic counting arrangement as set forth in claim 1 and including a'delay circuit, means responsive to the striking of said first tube in any stage for applying a pulse to said delay circuit, an output circuit for said delay circuit, and means consecutively connecting said output circuit to a corresponding one of the plurality of tubes in said plurality of successive stages.

3. A hunting circuit comprising a plurality of cascaded stages, each stage comprising first, second and third gridglow tubes, means for normally biasing said second gridglow tubes to fire upon application of a triggering pulse and said third grid-glow tubes to prevent their firing on application of such a triggering pulse, connections in circuit with said first grid-glow tubes for reversing the relative biases on said second and third tubes upon-the firing of said first tube, a plurality of outlet circuits connected respectively to be energized by the firing of the third tube in a corresponding stage, means associated with each of said outlet circuits for applying to said first tube of the corresponding stage marking potentials to permit firing thereof upon application of a triggering pulse if said outlet circuit is not energized and 'prevent such firing if energized, a common actuating circuit connected to apply a triggering pulse to said first tubes of all of said stages simultaneously, parallel input circuits in each stage for applying triggering pulses to the second and third tubes thereof simultaneously, connections from the second tube of each stage to the parallel input circuits of the succeeding stage, and means for applying a triggering pulse to the parallel input circuits ofsaid first stage upon the firing of the first tube of any of said stages, whereby a single actuating pulse applied to all of said tubes will first actuate one of said second or third tubes of the first stage and thereafter transfer actuation from stage to stage successively only until reaching a stage wherein said first tube has fired.

4. In a hunting circuit comprising a plurality of cascaded stages each associated with a separate outlet circuit, each stage comprising a gas discharge tube having a triggering electrode and an output electrode, a pair of relay means having a common input circuit and separate output circuits, a biasing network connected to both of said relay means for applying normal potentials thereto to permit a first one thereof to excite its output circuit upon application of an actuating pulse and to prevent the second thereof from so exciting its output circuit on the application of such actuating pulse, connections from the output electrode of said gas discharge tube for reversing the relative biases on said relay means upon the firing of said gas discharge tube, a connection from the first relay means of said pair to the common input circuit of the pair of relay means in the next succeeding stage, a connection from the second relay means of said pair to a corresponding outlet circuit, a circuit for applying an actuating pulse simultaneously to the gas discharge tubes of all of said stages, connections for applying marking potentials from the outlet circuit connecting to each stage to the corresponding gas discharge tube to prevent firing thereof if said outlet circuit is excited and permit firing of said tube if said outlet circuit is not excited, and means for applying an actuating pulse to the common input circuits of said relay means in said first stage on the firing of the grid glow tube of any of said stages.

5. An electronic hunting circuit comprising a plurality of stages connected in cascade, each stage including connections for attachment to an individual outlet line and each stage comprising at least one gas discharge tube connected to fire a like tube in a successive stage of the cascade so that the firing of the gas discharge tube in said first stage will cause the like tubes in successive stages to fire, means for applying to each stage a marking potential indicating that its associated outlet line is unoccupied, connections for applying a single actuating pulse simultaneously to all of said stages, means in each stage responsive to the concurrent application of such marking potential and an activating pulse for so biasing said gas discharge tube therein as to prevent its firing and thus firing the corresponding tubes in succeeding stages of the cascade, and means responsive to said single pulse to fire said gas discharge tube in said first stage.

6. An electronic hunting circuit comprising a plurality of stages connected in cascade, each stage including connections for attachment of an individual outlet line and each stage comprising at least one gas-discharge tube connected to fire a like tube in a successive stage of the cascade so that the firing of the gas-discharge tube in said first stage will cause the like tubes in successive stages to fire, means for applying to each stage a marking potential indicating that its associated outlet line is unoccupied, means in each stage responsive to the application of such marking potential for so biasing said gas-discharge tube therein as to prevent firing of the corresponding tubes in succeeding stages of the cascade, and means responsive to a single activating pulse to fire said gas discharge tube in said first stage.

References Cited in the file of this patent UNITED STATES PATENTS 2,664,555 Thomas et al Dec. 29, 1953 2,739,265 Six et a1 Mar. 20, 1956 2,783,415 Thomas et al Feb. 26, 1957 2,792,525 McArdle May 14, 1957 

